<?php

    /**
     * PHPExcel_Reader_Excel5_RC4
     * Copyright (c) 2006 - 2015 PHPExcel
     * This library is free software; you can redistribute it and/or
     * modify it under the terms of the GNU Lesser General Public
     * License as published by the Free Software Foundation; either
     * version 2.1 of the License, or (at your option) any later version.
     * This library is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     * Lesser General Public License for more details.
     * You should have received a copy of the GNU Lesser General Public
     * License along with this library; if not, write to the Free Software
     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
     * @category   PHPExcel
     * @package    PHPExcel_Reader_Excel5
     * @copyright  Copyright (c) 2006 - 2015 PHPExcel (http://www.codeplex.com/PHPExcel)
     * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
     * @version    ##VERSION##, ##DATE##
     */
    class PHPExcel_Reader_Excel5_RC4 {
        // Context
        protected $s = [];
        protected $i = 0;
        protected $j = 0;

        /**
         * RC4 stream decryption/encryption constrcutor
         * @param string $key Encryption key/passphrase
         */
        public function __construct($key) {
            $len = strlen($key);
            for ($this->i = 0; $this->i < 256; $this->i++) {
                $this->s[$this->i] = $this->i;
            }
            $this->j = 0;
            for ($this->i = 0; $this->i < 256; $this->i++) {
                $this->j           = ($this->j + $this->s[$this->i] + ord($key[$this->i % $len])) % 256;
                $t                 = $this->s[$this->i];
                $this->s[$this->i] = $this->s[$this->j];
                $this->s[$this->j] = $t;
            }
            $this->i = $this->j = 0;
        }

        /**
         * Symmetric decryption/encryption function
         * @param string $data Data to encrypt/decrypt
         * @return string
         */
        public function RC4($data) {
            $len = strlen($data);
            for ($c = 0; $c < $len; $c++) {
                $this->i           = ($this->i + 1) % 256;
                $this->j           = ($this->j + $this->s[$this->i]) % 256;
                $t                 = $this->s[$this->i];
                $this->s[$this->i] = $this->s[$this->j];
                $this->s[$this->j] = $t;
                $t = ($this->s[$this->i] + $this->s[$this->j]) % 256;
                $data[$c] = chr(ord($data[$c]) ^ $this->s[$t]);
            }
            return $data;
        }
    }
